Display screen or a portion thereof with a graphical user interface



FIG. 1 is a front view of a display screen or a portion thereof with agraphical user interface, showing a first embodiment of a new design;

FIG. 2 is a second embodiment thereof; and,

FIG. 3 is a third embodiment thereof.

The broken lines showing the display screen, and all other broken linesshowing portions of the graphical user interface, illustrate portions ofthe article and form no part of the claimed design. Shading indicates acontrast in visual appearance.

CLAIM The ornamental design for a display screen or a portion thereofwith a graphical user interface, as shown and described.